Active galactic nuclei (AGNs) are known to show flux variability over all observable
timescales and across the entire electromagnetic spectrum. Over the past decade, a growing …

Rapid, large amplitude variability at optical to X-ray wavelengths is now seen in an
increasing number of Seyfert galaxies and luminous quasars. The variations imply a global …

We present the results of a systematic search for quasars in the Catalina Real-time Transient
Survey exhibiting both strong photometric variability and spectroscopic variability over a …

Context. Changing-look active galactic nuclei (AGN) have been observed to change their
optical spectral type. Mrk 1018 is particularly unique: first classified as a type 1.9 Seyfert …

The changes of broad emission lines should be a crucial issue in understanding the
physical properties of changing-look active galactic nuclei (CL-AGNs). Here we present the …

In this paper, we present the long-term optical spectral monitoring of a changing-look active
galactic nucleus (AGN), NGC 3516, covering 22 yr (from 1996 to 2018). We explore a …

Accretion states, which are universally observed in stellar mass black holes in X-ray
binaries, might be expected in active galactic nuclei (AGN). This is the case at low …

Context. We analyze the broad Hβ line profile variability of a “changing look” active galactic
nucleus (CL-AGN) NGC 3516 over an extensive period of 25 years (from 1996 to 2021). The …

The hydrogen Balmer decrement (eg, Hα/Hβ) is widely adopted as an indicator of the
internal reddening of active galactic nuclei (AGNs). This is challenged by some low …

We present a comprehensive study of the changing-look active galactic nucleus (CL-AGN)
Mrk 1018 based on the largest dataset of optical, UV, and X-ray spectro-photometric data …